Lighting bulb



FIG. 1 is a perspective view of a lighting bulb showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a right side view thereof;

FIG. 6 is a top view thereof;

FIG. 7 is a bottom view thereof; and,

FIG. 8 is another perspective view thereof.

The broken line showings in the drawing are for illustrative purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a lighting bulb, as shown and described. 